This invention is concerned with an automatic horizontal plate freezer.
Presently machines of this type are well known and commonly used in the food processing industry to freeze large quantities of packaged products having generally, flat and parallel sides.
All horizontal plate freezers ensure the heat transmission due to the "direct contact" between the cold plates and the product: i.e., the heat is transmitted by "conduction". In these plate freezers means are provided for obtaining low temperature of plates, i.e. these latter are adequately cooled by a refrigerant circulating inside them.
When product is inserted between two cold plates, and is in contact with them, a double heat transmissin occurs due to this "double contact".
In order to embody the above principle, the plate freezers are all structured in such a way that, when they operate, first the plates are "opened" (i.e. sufficiently spaced apart from each other) for the introduction of the product, through an opening, and in the subsequent step they are "closed" again (i.e. approached to the product), to accomplish the "double contact", as described above. In all horizontal plate freezers, to properly apply the "double contact", the freezing plates are provided with spacers of proper height, either fixed or adjustable, housed in "U" channels located at the side edges of the plates, so that, in their closed position, said plates will be correctly placed parallel to each other and in contact with the product without damaging it.
It is obvious that spacers of correct height are to be employed because otherwise either damage to product or inefficient heat transmission would result.
In order to understand the scope of the present invention it is necessary to consider that the food processing industry often requires large quantities of frozen product in blocks, with very tight size and weight specifications; these blocks must guarantee maximum flatness and consistency being subject to further processing such as cutting in smaller portion, e.g. fish fingers, etc. To that purpose the loose product is introduced into strong metal frames, that give shape to the blocks. The frames are then placed into the machine that performs the freezing, and that, at the same time, has to apply pressure on the open side of the frames to obtain the desired shape.
After freezing, product is removed from the frames. At present, the only horizontal plate freezer suitable for these blocks are manually loaded and unloaded: their plates are opened, product is loaded, then plates are closed again and maintained under pressure for the necessary freezing time.
Clearly, such manual handling can hardly suit large production of blocks because of the labour costs involved and of short-comings of an intermittent running.
It is necessary to point out that present automatic freezers are designed in such a way that they cannot apply pressure on product, and therefore their use is limited to packaged products (mostly consumers packages), thus leaving out the vast applications of block freezing.